jwst flies thru artist concept image

Space Telescope

Webb will be the largest, most powerful and complex space telescope ever built and launched into space. It will fundamentally alter our understanding of the universe.

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About Webb:

view of webb's primary and secondary mirror in low light test

The James Webb Space Telescope (sometimes called JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the Hubble Space Telescope, with longer wavelength coverage and greatly improved sensitivity. The longer wavelengths enable Webb to look much closer to the beginning of time and to hunt for the unobserved formation of the first galaxies, as well as to look inside dust clouds where stars and planetary systems are forming today.

Key Facts:

Premier Observatory
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Webb will be the premier space observatory for astronomers worldwide, extending the tantalizing discoveries of the Hubble Space Telescope. About Compare Webb and Hubble
Largest Telescope in Space
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Webb will be the largest telescope ever placed in space; 100 times more powerful than Hubble. So big it has to fold origami-style to fit in the rocket and will unfold like a "Transformer" in space. Webb And Hubble Folding Mirrors
The First Stars and Galaxies
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With unprecedented infrared sensitivity, it will peer back in time over 13.5 billion years to see the first galaxies born after the Big Bang. Science Themes First Light Mather and BigBang
How Galaxies Assemble
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Webb will help astronomers to compare the faintest, earliest galaxies to today's grand spirals and ellipticals, helping us to understand how galaxies assemble over billions of years. Read More
Birth of Stars & Planetary Systems
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Webb will be able to see right through and into massive clouds of dust that are opaque to visible-light observatories like Hubble, where stars and planetary systems are being born. Read More
Exoplanets
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Webb will tell us more about the atmospheres of extrasolar planets, and perhaps even find the building blocks of life elsewhere in the universe. In addition to other planetary systems, Webb will also study objects within our own Solar System. Read More
Orbit
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Webb will orbit the sun, a million miles away from Earth at the second Lagrange point. (L2 is four times further away than the moon!) Read More
Launch
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Webb will launch in 2021 from French Guiana... (The mission lifetime is 5-10+ years.) Read More
Build, Integration & Test
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Webb has over 1200 skilled scientists, engineers and technicians from 14 countries and more than 29 US states as well as the District of Columbia building it. The Team. It is a joint NASA/ESA/CSA mission. Assembly and testing of the mirror and instruments occured at NASA Goddard.
Technology Innovations:
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Webb has created spinoff technologies. (Including a new LASIK-like procedure for your eyes!) Read More
Webb vs Hubble vs Spitzer
Webb vs other space telescope
Webb’s 18-segment primary mirror is over 6 times bigger in area than Hubble's and will be ~100x more powerful. (How big is it? approx 6.5 m in diameter) It has a secondary mirror nearly as big as Spitzer's primary... (The secondary mirror is 0.74 m in diameter. Spitzer's primary is 0.85 m in diameter.) Read More
Size:
Webb size
Webb is about half the size of a 737 yet less than 8% of the mass of a 737. It will be the biggest telescope ever launched into space. (Webb has a total mass of 6200 kg, the maximum mass of a 737 is 79,010 kg.) Read More
Sunshield and Temperature Extremes
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Thanks to the sunshield, the temperature is roughly 600 degrees Fahrenheit less on the cold, shaded side of the observatory than it is on the hot, sunlit side. Read More
Mirrors
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Webb’s primary mirror has 18 segments that work together as one; they can all be individually adjusted. Its segments have a mass of ~20 kg (44 lbs) each and are 4.3 feet tall. (You could lift one pretty easily.) Requires only about a golf ball's worth of gold coat for the huge primary mirror. (The coating is so thin that a human hair is 1000 times thicker!). Read More
Deployment
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Webb folds origami-style to fit in the Ariane 5 rocket; it unfolds once in space. (How small does it fold up? To about a quarter of its longest dimension so it fits in the 5m wide rocket.) Deployment Video
Operating Temperature
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Webb operates at just a few degrees above absolute zero! (Its operating temperature is under 50K, or -370F.) Video
Wavelengths
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Webb will see the universe in light invisible to human eyes. Though it sees primarily infrared light, it can also see red and gold visible light. (Webb’s wavelength range is 0.6 to 28.5 microns.) Read More
Sensitivity & Resolution
Sensitivity
Webb is so sensitive, it could detect the heat signature of a bumblebee at the distance of the moon, and can see details the size of a US penny at the distance of about 24 miles (40 km). (That's a limiting sensitivity of ~11 nJy and spatial resolution of better than 0.1 arc-secon at 2 microns.) Read More
Exoplanet Atmospheres
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Webb can see water vapor in extrasolar planet atmospheres. (If there were chlorofluorocarbons (CFCs) on an exoplanet, Webb would see them..) Read More

Site Highlights

Featured Images

technicians observe as one of Webb's primary mirror wings is openned for the last time on earth
Webb's Primary Mirror Deployed for the Last Time on Earth.

As part of the NASA’s James Webb Space Telescope’s final tests, the 6.5 meter (21 feet 4 inch) mirror was commanded to fully expand and lock itself into place, just like it would in space.
Read More: Webb’s Golden Mirror Wings Open One Last Time on Earth.

Image Details on Flickr | Downloadable Sizes.
Image Credit: NASA/Chris Gunn

technician on scaffolding approaches Webb's primary mirror wing
View 2: Webb Successfully Executes Commands To Deploy Its Primary Mirror

Another shot of the successful recent mirror deployment test. The conclusion of this test represents the team’s final checkpoint in a long series of tests designed to ensure Webb’s 18 hexagonal mirrors are prepared for a long journey in space, and a life of profound discovery. After this, all of Webb’s many movable parts will have confirmed in testing that they can perform their intended operations after being exposed to the expected launch environment. Image credit: NASA/Chris Gunn.

Making the testing conditions close to what Webb will experience in space helps to ensure the observatory is fully prepared for its science mission one million miles away from Earth.

Commands to unlatch and deploy the side panels of the mirror were relayed from Webb’s testing control room at Northrop Grumman, in Redondo Beach, California. The software instructions sent, and the mechanisms that operated are the same as those used in space. Special gravity offsetting equipment was attached to Webb to simulate the zero-gravity environment in which its complex mechanisms will operate. All of the final thermal blanketing and innovative shielding designed to protect its mirrors and instruments from interference were in place during testing.

Image Details on Flickr | Downloadable Sizes
Image Credit: NASA/Chris Gunn

View from above with Tech in foreground of Webb's Sunshield Successfully Unfolds and Tensions in Final Tests
NASA’s Webb Sunshield Successfully Unfolds and Tensions in Final Tests

Prior to the successful mirror deployment test, #NASAWebb cleared one of its most important testing milestones to date. Webb’s 5-layer sunshield was successfully deployed and tensioned into the same configuration it will have once in space!

Image Details on Flickr | Downloadable Sizes
Image Credit: NASA/Chris Gunn

low angle view of Webb's Sunshield Successfully Unfolds and Tensions in Final Tests
View 2: Webb's Sunshield Successfully Unfolds and Tensions in Final Tests

Another shot of the successful recent sunshield test. Webb is now in its final series of deployment and checkout tests before the observatory is packed for shipment to French Guiana for launch aboard an @ArianeGroup Ariane V rocket. These tests will verify that Webb will deploy perfectly in space after its launch. Image credit:

Image Details on Flickr | Downloadable Sizes
Image Credit: NASA/Chris Gunn

Site Highlights

Featured Videos

Webb Mirror Beauty

This video shows the James Webb Space Telescope's mirrors during their long string of tests, from individual segments to the final tests of the assembled mirror. Read more about our latest milestone, the mirrors last unfolding on Earth. The next time will be in space!

Download this video plus additional B-roll.
Credits: NASA's Goddard Space Flight Center

The James Webb Space Telescope's Folding Mirrors

Webb's primary mirror has been deployed in 2 recent tests, most recently in May 2021, and previously in March 2021 which the above video shows. The tests involved commanding the spacecraft’s internal systems to fully extend and latch Webb’s iconic 6.5 meter (21 feet 4-inch) primary mirror.

“Deploying both wings of the telescope while part of the fully assembled observatory is another significant milestone showing Webb will deploy properly in space. This is a great achievement and an inspiring image for the entire team,” said Lee Feinberg, optical telescope element manager for Webb at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Download this video.
Credits: NASA's Goddard Space Flight Center

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Featured Content

jwst art show
#jwstArt Webb ART & SCIENCE
Twenty two artists were selected nationwide to attend the James Webb Space Telescope Artist Event at NASA's Goddard Space Flight Center in Greenbelt, Md. This gallery shows their impressions of the Webb Telescope and its mission.